Copious means there is a lot of something — a large amount, more than a little, often more than you strictly need. We say copious notes (you wrote and wrote), copious rain, copious amounts of food. It sounds a little formal and bookish; in ordinary talk a student is more likely to say a lot of or lots of. Teachers and textbooks like it because it is neat and strong. It comes from Latin copia, “abundance, plenty,” through copiosus, “full of plenty.” On the surface it looks like copy + -ous, but that is only how the English word is shaped to the eye. The real old idea is “plenty,” not “make a duplicate.”